Reborn picks up a couple of decades after The Keep. Glaeken has finally been allowed to age normally when suddenly Rasalom re-enters the picture as the unborn baby of an innocent woman and her husband, the world's first clone. The Ally wants to destroy him and the Adversary has agents on-hand to protect him at all cost.
Wilson has fun here spinning out his Secret History of the World, and warping the religions of the world--particularly Catholicism--around it. Aside from that, it's pretty generic horror fare.